I don't think it is a forsythia. It's only flowers are small like the ones you can barely see in the photos and they appeared after the leaves. The stems are not hollowForsythia. Look for hollow stems.
It really fits the description. Thanks a lot. I would have never found it on my ownits Euonymus europaeus - Spindle tree!
Ah so....Nope not Forsythia, its Euonymus europaeus - Spindle tree!
Are you sure it's not dead? Check under the bark.The last image was taken in winter color
I didn't look at the file names ;-) Now I know how this species looks like in Winter.That picture was taken in february. The others were taken today. It stayed outside last winter, it even went through nights with lower temperatures than -20C.